Hello Friend, thanks for reaching out here for help. Yes depression, sleep, concentration are interlinked problem. If you are interested in solving this, you need to first figure out what is causing the depression. If you worry too much about any past bad incidents, loss in family, sadness etc, then you can tag your problem as depression. Once narrowed with the root cause you can work on possible solutions. If you can't do this analysis yourself, then take the professional help of psychology counselor.